CVE-2026-47698 in vm2
Summary
by MITRE • 08/18/2026
vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.6, lib/bridge.js and lib/setup-sandbox.js fail to block stacked indirection through Function.prototype.call around dangerous host prototype getter and setter mutators, allowing sandbox code to sever a host intrinsic's prototype chain and reach e.constructor.constructor for arbitrary host command execution. This issue is fixed in version 3.11.6.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified in the vm2 library prior to version 3.11.6 represents a critical failure in sandbox isolation mechanisms, specifically within the JavaScript virtual machine environment used by Node.js applications. The core of this issue lies in how the library handles prototype chains and function invocation contexts when executing untrusted code. In standard JavaScript execution environments, objects possess prototypes that define their behavior and properties. Security sandboxes rely on strict boundaries to prevent sandboxed code from accessing or modifying host-level intrinsics such as global objects, constructors, and built-in methods. However, the implementation in lib/bridge.js and lib/setup-sandbox.js failed to adequately restrict stacked indirection through Function.prototype.call. This oversight allowed malicious actors to manipulate the execution context of functions, effectively bypassing the intended isolation layers that separate sandboxed code from the host environment.
The technical flaw centers on the ability to sever a host intrinsic's prototype chain using carefully crafted function calls. By leveraging dangerous host prototype getter and setter mutators, an attacker could perform stacked indirection operations that alter how properties are resolved during runtime. Specifically, this manipulation enables the retrieval of e.constructor.constructor from within the sandboxed context. In JavaScript, accessing constructor functions allows for the creation of new Function objects, which can execute arbitrary strings as code. This mechanism effectively grants the sandboxed environment full access to Node.js's global scope and execution capabilities, transforming a contained virtual machine into an unrestricted command execution vector. The vulnerability exploits the dynamic nature of JavaScript prototypes, where modifying or accessing prototype chains in unexpected ways can lead to privilege escalation within the application process.
From an operational perspective, this vulnerability poses severe risks to applications relying on vm2 for code isolation. If exploited, it allows arbitrary host command execution, which typically leads to complete system compromise depending on the privileges of the Node.js process running the sandboxed code. Attackers could read sensitive configuration files, exfiltrate data from memory, install backdoors, or pivot further into internal networks if the server is exposed. The impact is particularly acute in environments where vm2 is used to execute user-supplied scripts, such as in online coding platforms, template engines, or automated testing frameworks that process untrusted input. Because the vulnerability allows for arbitrary code execution rather than just information disclosure, it is classified as a high-severity issue requiring immediate remediation.
This flaw aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command and CWE-204 Observable Response Discrepancy in Security-Related Control when the sandbox fails to enforce its boundaries correctly. In terms of attack tactics, it relates to MITRE ATT&CK techniques involving code execution within a container or virtualized environment, specifically leveraging script interpreter abuse. The exploitation path demonstrates how improper handling of object prototypes and function contexts can undermine security controls designed to isolate untrusted code. Developers must recognize that sandboxing is not absolute and requires rigorous validation of all interactions with host intrinsics, particularly those involving prototype manipulation and dynamic function construction.
The recommended mitigation is straightforward: upgrade the vm2 library to version 3.11.6 or later, where these specific checks for stacked indirection through Function.prototype.call have been implemented. This update addresses the failure to block dangerous host prototype getter and setter mutators that were previously exploited to sever prototype chains. In addition to upgrading dependencies, organizations should review their use of vm2 to ensure it is only used in contexts where untrusted code execution is strictly necessary and isolated from critical system resources. Implementing additional defense-in-depth measures such as running Node.js processes with minimal privileges can further reduce the impact if a future vulnerability were to be discovered. Regularly auditing third-party dependencies for known vulnerabilities remains essential, especially when those components are responsible for security-critical isolation tasks like sandboxing user input or scripts.